The invention relates to a packing for heat exchange and material exchange (mass transfer) columns with a multiplicity of generally vertically arranged corrugated plates (or strips) having their side surfaces adjacent one another and whose adjacent ribs run from top to bottom in a generally arcuate pattern whereby the ribs of two adjoining plates cross each other.
In distillation, absorption, gas scrubbing and similar operations in process technology, columns are used which contain baffles for the heat exchange and mass transfer exchange between liquid and gas. These baffles are comprised either of trays, for example bubble trays, tunnel trays, sieve trays or valve trays, of randomly arranged packings like for example Raschig rings, Pall rings or saddles, or of ordered packings in various geometric configurations.
With ordered packings the geometries of cross channel structures have ranged widely in technological applications. As is generally the case with packed columns, maximum capacity with ordered packing is also limited in the cross-channel structure by the development of a flooded state. The visual observation of the flooded state in distillation columns which are equipped with packings of a cross channel structure which shows that the flooding always develops at the lower edge of the individual packing layers. In order to increase productivity of such packings, one seeks to modify the lower edge of the individual packing layers and partly in addition the upper edge of the individual packing layers so at to increase the attainable throughput of liquid and gas.
In EP 858 830 A1 it is proposed to increase the spacing of neighboring packing elements at the lower edge of the packing layers by there reducing the bend height. As a further possibility a partial or complete removal of a part of the material, for example at every second packing element from the lower end of the packing layer. The drawback of this approach is that it affects the separating efficiency and causes deterioration in the mechanical strength of the packing.
The alternative possibility is protected in WO 97/16247 in which the geometry of the cross-channel structure is altered. The bends are no longer straight as is customarily the case, but rather are of S shape configuration and are so arranged that the short column orientation at the lower and upper ends of the packing layers run approximately vertically. The fabrication of this packing is expensive. A drawback is that over the packing height there are small lateral offsets of the flow passages through the vertically-running lower and upper ends. This reduces the desired lateral transverse mixing of the gas flow. To compensate for this drawback, additional liquid collectors and distributors must be optionally provided to limit the problematical distributions.
DE 39 18 483 describes a packing with a variable height geometry in which the short columns of the cross-channel structure run substantially vertically and parallel to one another at the lower end and are increasingly bent toward the horizontal upwardly. In order to provide at the lower region of the packing layer, a sufficient mechanical stability in the bends between neighboring corrugations or folds, planar sections are provided. Here as well a damming up of liquid should be avoided.
A packing with a cross-channel structure is described in DE 29 21 270 C2 in which the folds have an arcuate path. The individual plates are alternatively so mounted that the greater flow resistance lies alternately upwardly and downwardly so that in this construction there is no shift of the flooding state to higher loadings. Further packings with nonlinear fold paths are described in DE 12 93 796, DE 12 87 096, FR 14 79 375 and GB 10 80 991.
The object of the invention is to provide an ordered packing which can have an increased throughput by comparison with the known packing in cross-channel structures.
This object is achieved according to the invention in that the ribs in the upper region of a plate are straight and inclined to the upper, especially horizontal plate edge and in the lower region of the plate run with an arcuately curved pattern.
Such a packing produces an especially high throughput at an optimal efficiency. The structure is simple and enables inexpensive manufacture and simple mounting.